<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    input{
      margin: auto 0;
      width: 100px;
      /*间隔*/
      margin-bottom: 10px;
      /*空间*/
      padding: 10px;
      font-size: 15px;
      /*拐角*/
      border-radius: 4px;
    }
    .but{
      width: 150px;
      padding: 10px;
      background-color: aquamarine;
    }
  </style>
</head>
<body>
  <div style="background-color: aquamarine;width: 400px;height: 300px;text-align: center;margin: 0 auto;margin-top: 200px">
    <h1 style="text-align: center">Login</h1>
    <input type="text" placeholder="用户名"><br>
    <input type="password" placeholder="密码"><br>
    <button class="but" type="submit">登录</button>
    <button class="but" type="submit">注册</button>
  </div>
</body>
</html>